Re: [PATCH v6] can: virtio: Add virtio CAN driver

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Oct 29, 2025 at 06:40:45PM +0100, Matias Ezequiel Vara Larsen wrote:
> Add virtio CAN driver based on Virtio 1.4 specification (see
> https://github.com/oasis-tcs/virtio-spec/tree/virtio-1.4). The driver
> implements a complete CAN bus interface over Virtio transport,
> supporting both CAN Classic and CAN-FD Ids. In term of frames, it
> supports classic and CAN FD. RTR frames are only supported with classic
> CAN.
> 
> Usage:
> - "ip link set up can0" - start controller
> - "ip link set down can0" - stop controller
> - "candump can0" - receive frames
> - "cansend can0 123#DEADBEEF" - send frames
> 
> Signed-off-by: Harald Mommer <harald.mommer@oss.qualcomm.com>
> Signed-off-by: Mikhail Golubev-Ciuchea <mikhail.golubev-ciuchea@oss.qualcomm.com>
> Co-developed-by: Marc Kleine-Budde <mkl@pengutronix.de>
> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
> Cc: Damir Shaikhutdinov <Damir.Shaikhutdinov@opensynergy.com>
> Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com>
> ---
> V6:
> * Address nits (see
>   https://lore.kernel.org/all/aO0JjDGk2zLlzB1E@fedora/T/#mc7221192856d557da9c0da2b47e4343dfea0ca2f)
> * Check for error during register_virtio_can()
> * Remove virtio_device_ready()
> * Allocate virtio_can_rx rpkt[] at probe
> * Define virtio_can_control struct
> * Return VIRTIO_CAN_RESULT_NOT_OK after unlocking
> * Define sdu[] as a flex array for both tx and rx. For rx, use
>   VIRTIO_CAN_F_CAN_FD to figure out the max len for sdu
> * Fix statistics in virtio_can_read_tx_queue() and
>   how we indicate error to the user when getting
>   VIRTIO_CAN_RESULT_NOT_OK
> * Fix syntax of virtio_find_vqs()
> * Drop tx_list
> * Fix values of VIRTIO_CAN_F_LATE_TX_ACK and VIRTIO_CAN_F_RTR_FRAMES
> * Tested with vhost-device-can
>   (see
>   https://github.com/rust-vmm/vhost-device/tree/main/vhost-device-can)
>   and qemu (see
>   https://github.com/virtualopensystems/qemu/tree/vhu-can-rfc) 
> 
> V5:
> * Re-base on top of linux-next (next-20240103)
> * Tested with https://github.com/OpenSynergy/qemu/tree/virtio-can-spec-rfc-v3
> 
> RFC V4:
> * Apply reverse Christmas tree style
> * Add member *classic_dlc to RX and TX CAN frames
> * Fix race causing a NETDEV_TX_BUSY return
> * Fix TX queue going stuck on -ENOMEM
> * Update stats.tx_dropped on kzalloc() failure
> * Replace "(err != 0)" with "(unlikely(err))"
> * Use "ARRAY_SIZE(sgs)"
> * Refactor SGs in virtio_can_send_ctrl_msg()
> * Tested with https://github.com/OpenSynergy/qemu/tree/virtio-can-spec-rfc-v3
> 
> RFC V3:
> * Incorporate patch "[PATCH] can: virtio-can: cleanups" from
>   https://lore.kernel.org/all/20230424-footwear-daily-9339bd0ec428-mkl@pengutronix.de/
> * Add missing can_free_echo_skb()
> * Replace home-brewed ID allocator with the standard one from kernel
> * Simplify flow control
> * Tested with https://github.com/OpenSynergy/qemu/tree/virtio-can-spec-rfc-v3
> 
> RFC V2:
> * Remove the event indication queue and use the config space instead, to
>   indicate a bus off condition
> * Rework RX and TX messages having a length field and some more fields for CAN
>   EXT
> ---
>  MAINTAINERS                     |    7 +
>  drivers/net/can/Kconfig         |   12 +
>  drivers/net/can/Makefile        |    1 +
>  drivers/net/can/virtio_can.c    | 1022 +++++++++++++++++++++++++++++++
>  include/uapi/linux/virtio_can.h |   78 +++
>  5 files changed, 1120 insertions(+)
>  create mode 100644 drivers/net/can/virtio_can.c
>  create mode 100644 include/uapi/linux/virtio_can.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 80cd3498c293..14a738b8ecb2 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -27068,6 +27068,13 @@ F:	drivers/scsi/virtio_scsi.c
>  F:	include/uapi/linux/virtio_blk.h
>  F:	include/uapi/linux/virtio_scsi.h
>  
> +VIRTIO CAN DRIVER
> +M:	"Harald Mommer" <harald.mommer@oss.qualcomm.com>
> +L:	linux-can@vger.kernel.org
> +S:	Maintained
> +F:	drivers/net/can/virtio_can.c
> +F:	include/uapi/linux/virtio_can.h
> +

So how will maintainance look like for this?
Don't you want to co-maintain it, given you are submitting it?
The maintainer is supposed to interact with linux.


Probably a good idea to have this under
VIRTIO CORE AND NET DRIVERS

at least additionally, or alternatively add
L:	virtualization@lists.linux.dev



>  VIRTIO CONSOLE DRIVER
>  M:	Amit Shah <amit@kernel.org>
>  L:	virtualization@lists.linux.dev
> diff --git a/drivers/net/can/Kconfig b/drivers/net/can/Kconfig
> index d43d56694667..7b5806f11853 100644
> --- a/drivers/net/can/Kconfig
> +++ b/drivers/net/can/Kconfig
> @@ -217,6 +217,18 @@ config CAN_XILINXCAN
>  	  Xilinx CAN driver. This driver supports both soft AXI CAN IP and
>  	  Zynq CANPS IP.
>  
> +config CAN_VIRTIO_CAN
> +	depends on VIRTIO
> +	tristate "Virtio CAN device support"
> +	default n
> +	help
> +	  Say Y here if you want to support for Virtio CAN.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called virtio-can.
> +
> +	  If unsure, say N.
> +
>  source "drivers/net/can/c_can/Kconfig"
>  source "drivers/net/can/cc770/Kconfig"
>  source "drivers/net/can/ctucanfd/Kconfig"
> diff --git a/drivers/net/can/Makefile b/drivers/net/can/Makefile
> index 56138d8ddfd2..2ddea733ed5d 100644